Synthesis and characterization of chiral benzylic ether-bridged periodic mesoporous organosilicas

The first synthesis of a chiral periodic mesoporous organosilica (PMO) carrying benzylic ether bridging groups is reported. By hydrolysis and condensation of the new designed chiral organosilica precursor 1,4-bis(triethoxysilyl)-2-(1-methoxyethyl)benzene (BTEMEB) in the presence of the non-ionic oligomeric surfactant Brij 76 as supramolecular structure-directing agent under acidic conditions, an ordered mesoporous chiral benzylic ether-bridged hybrid material with a high specific surface area was obtained. The chiral PMO precursor was synthesized in a four-step reaction from 1,4-dibromobenzene as the starting compound. The evidence for the presence of the chiral units in the organosilica precursor as well as inside the PMO material is provided by optical activity measurements.     

Synthesis of large-pore methylene-bridged periodic mesoporous organosilicas and its implications

In this article, we report the synthesis of methylene-bridged periodic mesoporous organosilicas (PMOs) of the SBA-15 type. The materials were characterized by SAXS, BET, NMR, FESEM, and TEM. It was found that the synthesis of methylene-bridged SBA-15 PMOs requires more rigorous conditions than that of SBA-15 PMOs bearing organic bridges other than methylene. A mild acidic environment, which slows down the hydrolysis and condensation rates of the precursor, with the assistance of a salt, which enhances precursor-template interaction, should be used to synthesize high-quality large-pore methylene-bridged PMOs. We attributed this to the fast hydrolysis and condensation rates and the rigid backbone of precursor 1,2-bis(triethoxysilyl)methylene. By examining and comparing the synthesis of three large-pore PMOs with different bridges, we concluded that the inductive, bridging, and conformation effects of the organic bridging group play an important role in the synthesis of large-pore PMO materials.     

Morphologies of large-pore periodic mesoporous organosilicas

In this article, we report a systematic investigation on the morphologies of SBA-15 type large-pore periodic mesoporous organosilicas templated by the block copolymer P123. By tuning synthetic parameters such as stirring, acidity, reaction ratio, reaction duration, and autoclaving, a wide spectrum of unique primary particle morphologies, such as the spindle-, pearl-, diamond-, rod-, and platelike particles, and nanoparticles has been prepared. These primary particles were found to self-assemble in solution to form various large hierarchical macrostructures, such as mesostructured necklaces and cobweb-supported necklaces. The assembling process was elucidated with the information observed at different stages of reaction. Stirring, reaction duration, and autoclaving were identified to be the key factors affecting the efficiency and degree of the self-assembly process. A nucleation-accretion mechanism for the formation of various PMO primary particles was proposed by examining the relation between the external morphologies and the underlying mesostructure.     

Synthesis and characterization of periodic mesoporous organosilicas from bridged organosilanes in the presence of mixed salts

A simple but effective synthetic pathway to periodic mesoporous organosilicas (PMOs) has been put forward in this article. The novelty of the present preparative route lies in that, for specific examples, highly ordered ethane- and benzenesilica PMOs can be facilely prepared in the presence of an inorganic salt pair within a wide compositional range, where no addition of mineral acids was necessary. Most of interest is that crystal-like pore walls were observed for the large-pore benzenesilica PMO promoted by this novel system, which has rarely been reported for copolymer-assembled organosilicas, even though the degree of molecular order is not as perfect as those benzenesilicas prepared under basic conditions utilizing cationic surfactants as template. Characterization results based on a series of techniques indicated that both inorganic salts are important for the assembly of ordered mesostructures under the present system, and a plausible formation mechanism deduced from the “salt-assisted” concept as previously reported for mesoporous nonsiliceous materials was discussed.     

Adsorption behavior of nicotine on periodic mesoporous organosilicas

In this study, we focused on the adsorption of nicotine from aqueous solution such as water and simulated body fluids (SBFs), where SBF has ion concentrations approximately equal to those of human blood plasma. We prepared periodic mesoporous organosilica (PMO) materials as adsorbents from 4,4-bis(triethoxysilyl)biphenyl (BTES-biphenyl), 1,4-bis(triethoxysilyl)benzene (BTES-benzene) and bis[3-(trimethoxy silyl)propyl]amine (BTMS-amine) as precursors and investigated on their adsorption behavior of nicotine as a guest material under different solvent conditions. For this work, two different kinds of SBF, c-SBF and r-SBF, have been chosen, where c-SBF is a transitional SBF solution, and r-SBF is a modified SBF solution that is closer to human blood plasma. Adsorption of nicotine on PMOs has been characterized by a UV-Vis spectroscopy. The adsorption behavior was strongly dependent on the isoelectric point and hydrophobicity of the PMO as well as the hydrophobicity of nicotine.     

Novel route to periodic mesoporous aminosilicas, PMAs: ammonolysis of periodic mesoporous organosilicas

A new route to periodic mesoporous aminosilicas (PMAs) that contain amine functional groups in the framework of a mesoporous network is reported. The materials are prepared via thermal ammonolysis of periodic mesoporous organosilicas (PMOs) under a flow of ammonia gas. PMOs integrate similar or even higher quantities of nitrogen-containing groups upon ammonolysis than similarly treated ordered mesoporous silicas (MCM-41). The quantity of amine groups introduced into the materials was found to depend strongly on the ammonolysis temperature. The largest loading of amine groups was obtained when a well-ordered cubic methylene PMO material without prior vacuum-drying was thermolyzed in ammonia. The ordered mesoporosity of PMOs was preserved during the ammonolysis with only a slight decrease in the mesopore size and the degree of mesostructural ordering. The extent of substitution of framework oxygen by amine and nitride groups was established by solid-state (29)Si CP-MAS, (29)Si MAS, (15)N MAS, and (13)C CP-MAS NMR spectroscopies, elemental analysis, and X-ray photoelectron spectroscopy. In some cases, methylene and methyl functional groups were also present in the PMAs along with amine functional groups, as inferred from elemental analysis and gas adsorption, particularly in cases where PMOs were subjected to ammonolysis at 400 and 550 degrees C for several hours. This resulted in new multifunctional mesoporous organoaminosilica nanomaterials with properties that could be tuned by systematically varying the relative amounts of hydrophilic amine and hydrophobic hydrocarbon pendent and framework groups. The stability upon storage was found to be much higher for PMAs obtained from PMOs than for those obtained from MCM-41 silicas under the same conditions.     

Functionalized periodic mesoporous organosilicas: Hierarchical and chiral materials

The integration of organic and inorganic fragments within the pore walls of the periodic mesoporous organosilicas (PMOs) represents one of the recent breakthroughs in material science. The resulting PMOs are promising materials for applications in such areas as catalysis, adsorption, separation and drug-delivery. We summarize here the recent progress made in the synthesis of PMOs with hierarchical structures and large functional groups, with special emphasis on the chiral mesoporous organosilicas and their ...     

Underquaternized anion exchange resins as covalent scavengers

The use of partially quaternized, chloromethylated polystyrene as a covalent scavenger of cholate ion in aqueous media has been demonstrated. The ability of such polymers to scavenge organic anions by covalent as well as by ionic means has important implications in the areas of medicinal and environmental chemistry, which are briefly discussed.     

离子交换树脂催化合成碳酸亚丙酯

碘型离子交换树脂在某些偶极非质子性溶剂的作用下，能有效地催化二氧化碳与环氧丙烷合成碳酸亚丙酯，并能重复使用至少10次而仍能保持较高的催化活性。     

Ultra-fast hydrothermal synthesis of diastereoselective pure ethenylene-bridged periodic mesoporous organosilicas

A novel synthesis of diastereoselective pure periodic mesoporous ethenylene-silicas is presented, using (a) the homemade E-diastereoisomer of bis(triethoxysilyl)ethene, (b) a more efficient extraction procedure of the template P123 and (c) an ultra-fast synthesis procedure.     

Neutron scattering study of water confined in periodic mesoporous organosilicas

A series of quasi-elastic neutron scattering measurements were performed using IN6 at the Institute Laue Langevin for a mesoporous organosilica material with phenyl functions, called phenyltriethoxysilane (PTES). The aim of the experiment was to study the diffusion dynamics of nano-scale water clusters inside the hydrophobic pores as a function of temperature and hydration. By fitting the Debye-Waller factor, the data show clearly the different behavior between water, both inside and outside the hydrophobic pores, which resembles bulk water. The mean thermal displacement 〈u²〉 of the external water increases with T almost linearly up to 353 K, while the internal water quickly reaches the maximum at T∼323 K, indicating the confinement by an averaged pore diameter of the porous organosilica.     

Synthesis and lysozyme adsorption of rod-like large-pore periodic mesoporous organosilica

Highly ordered rod-like large-pore periodic mesoporous organosilica (PMO) was successfully synthesized at low acid concentration with the assistance of inorganic salt using triblock copolymer P123 as a template. The roles of inorganic salt and acidity in the production of highly ordered mesostructure and the morphology control of PMOs were investigated. It was found that the inorganic salt can significantly widen the range of the synthesis parameters to produce highly ordered 2D hexagonal pore structure of p6mm symmetry. However, the uniform rod-like PMOs can only be synthesized in a narrow range of acid and salt concentrations, which were sensitive to induction time. The adsorption of lysozyme on PMO was studied at different pH values in comparison with adsorption on pure silica material under controlled morphology and pore structure. It was found that the adsorption capacity of lysozyme on the PMO was lower than that on pure SBA-15 silica material and the adsorption amounts are larger at pH 9.6 than at 7.0 for both materials. The results show that the electrostatic interaction between lysozyme and PMO/SBA-15 surface is more dominant than the hydrophobic forces and the interaction of neighboring lysozyme molecules also plays an important role.     

Phase transformation of the periodic mesoporous organosilicas assisted by organotrialkoxysilane

A phase transformation of mesoporous organosilicas from 2D-hexagonal P6mm to cubic Pm3n phase can be induced by the organotrialkoxysilane with hydrophilic pendant group with the aid of methanol during the co-condensation of 1,2-bis(trimethoxysilyl)ethane (BTME) and (EtO)(3)Si-R (R = L-prolinamide, trans-(1R,2R)-diaminocyclohexane, and gamma-aminopropyl) using the cationic surfactant, octadecyltrimethylammonium chloride (C(18)TMACl), as template in basic medium. Under similar synthesis conditions, no cubic Pm3n phase could be formed in the absence of (EtO)(3)Si-R. Depending on the type of the pendant group, different amounts of methanol were needed for the formation of the cubic Pm3n phase. N-[(triethoxysilyl)propyl]-L-prolinamide (M(L-Pro)) could easily induce the phase changing from 2D-hexagonal P6mm to cubic Pm3n phase probably because L-proline could result in a decreasing of the surfactant packing factor (g) through formation of large architecture on the outer boundary of the surfactant micelles. The organotrialkoxysilane can also help the formation of spherical morphology of the resultant materials.     

Face-centered-cubic large-pore periodic mesoporous organosilicas with unsaturated and aromatic bridging groups

Large-pore ethenylene-bridged (-CH═CH-) and phenylene-bridged (-C(6)H(4)-) periodic mesoporous organosilicas (PMOs) with face-centered-cubic structure (Fm3m symmetry) of spherical mesopores were synthesized at 7 °C at low acid concentration (0.1 M HCl) using Pluronic F127 triblock copolymer surfactant in the presence of aromatic swelling agents (1,3,5-trimethylbenzene, xylenes-isomer mixture, and toluene). In particular, this work reports an unprecedented block-copolymer-templated well-ordered ethenylene-bridged PMO with cubic structure of spherical mesopores and an unprecedented block-copolymer-templated face-centered cubic phenylene-bridged PMO, which also has an exceptionally large unit-cell size and pore diameter. The unit-cell parameters of 30 and 25 nm and the mesopore diameters of 14 and 11 nm (nominal BJH-KJS pore diameters of 12-13 and 9 nm) were obtained for ethenylene-bridged and phenylene-bridged PMOs, respectively. Under the considered reaction conditions, the unit-cell parameters and pore diameters were found to be similar when the three different methyl-substituted benzene swelling agents were employed, although the degree of structural ordering appeared to improve for phenylene-bridged PMOs in the sequence of decreased number of methyl groups on the benzene ring.     

Spectroscopic evidence of thermally induced metamorphosis in ethenylene-bridged periodic mesoporous organosilicas

Spectroscopic evidence of the thermally induced generation of multifunctional mesoporous materials through metamorphism within the pore walls of ethenylene-bridged PMOs is presented.     

Synthesis of diamine functionalized mesoporous organosilicas with large pores

Hybrid mesoporous silicas functionalized with ethylenediamine groups have been synthesized via sol–gel process under different conditions. The best textural properties, with pore diameters up to 170 Å, have been obtained using carboxylic acids as catalysts in propanol as solvent without the need for any surfactant. The presence of the diamine moiety has been demonstrated by different characterization techniques, and the materials have been used in the adsorption of copper cations. The adsorption capacity of all the solids is high (up to 1.87 mmol/g and up to 2.47 Cu atoms/nm²), with important variations in the properties of the silica surface, besides the role of the immobilized diamine moieties as ligand for copper. In general the surface area seems to be the most important feature controlling the adsorption.     

Synthesis and characterization of mesoporous alumina,and adsorption performance for n-butane

Research on Chemical Intermediates - Samples of mesoporous alumina were synthesized by the sol–gel method, using carbohydrate as template and aluminium isopropoxide as the source of...     

Synthesis and characterization of pyridyl anion exchange resin for 99Tc removal

Journal of Radioanalytical and Nuclear Chemistry - A new pyridyl anion exchange resin (PS-N) was synthesized by chloroacetylation and quaternization on the polystyrene-divinylbenzene microspheres...